Graduate Student Western University London, Ontario, Canada
Abstract Body : Background: Approximately 60% of patients undergoing breast cancer surgery experience acute postoperative pain (APP) that is primarily localized to the axilla. Postoperative analgesia is often managed with intraoperative peripheral nerve blocks (PNBs), a form of regional anesthesia. The PNBs typically administered in breast surgery target the intercostobrachial nerve (ICBN), which provides sensory innervation to the axilla. Therefore, axillary APP could be due to additional, undocumented innervation pathways. The current study aims to expand sensory nerve identification via anatomical dissection.
Methods: Seven axillary dissections (3F, 4M) were performed with donors supine and upper limbs abducted. Incisions along the anterolateral thorax and superior clavicle created laterally reflecting skin flaps deep to pectoralis minor, allowing visualization of the ICBN and brachial plexus. Scaled photographic images were taken during dissections for documentation.
Preliminary Results: In each dissection, an ICBN (100%, n=7) and a branch of the posterior cord (posterior cord branch: PCB; 100%, n=7) were identified entering axillary subcutaneous tissue. In 57% of dissections (n=4), a branch of the medial cord (medial cord branch: MCB) was identified. The ICBN remained localized to the anterior axillary base but demonstrated various extrathoracic branching patterns: a single origin, dual origins, and double ICBNs. The PCB demonstrated variable branching patterns but was consistent in its origin and distribution. Arising proximally on the posterior cord, the PCB coursed inferiorly, remaining deep to the axillary vessels, before crossing beneath the axillary vein and penetrating axillary subcutaneous tissue along the posterior axillary base. Finally, when present, the MCB arose from the proximal medial cord and travelled inferiorly, crossing beneath the axillary vein before penetrating axillary subcutaneous tissue along the midaxillary line.
Conclusion: In addition to the ICBN, two previously undocumented branches of the brachial plexus have been identified entering the subcutaneous tissue of the axilla. While previous studies investigating the brachial plexus describe the variability of the well-documented branches of the cords, neither the PCB nor the MCB can be characterized as such due to their individual origins on the cords and their distal axillary innervation sites.
Significance: The current anatomical study enhances the understanding of axillary sensory innervation and could contribute to the development of more comprehensive PNBs for breast cancer surgery. Such techniques could greatly reduce APP and eliminate the need for postoperative opioids, thereby promoting surgical success and reducing post-surgical morbidity.
